What has eight eyes, white stripes and can fire up a dance floor? 

It was the month of March in 2023 in Montevideo, Uruguay, and Divya Uma was getting ready to present her work on social spiders at the International Congress of Arachnology. Far away from home in Bengaluru, she was pleasantly surprised to bump into two other Indians: fellow behavioural ecologist Dinesh Rao, from Universidad Veracruzana in Mexico, and Kiran Marathe, a graduate student at the University of British Columbia in Canada. Not only were Dinesh and Kiran her compatriots, but it turned out that all three of them were Kannada-speakers, too. ​“What are the odds of three Kannadigas working on spiders meeting in South America?” Kiran laughs. This had to be a sign that a collaboration was meant to be. 

Just a year before the meeting, Kiran had discovered three new species of jumping spiders in India’s Deccan Plateau. He had noted then, that these spiders — from a genus called Stenaelurillus — indulged in strikingly complex courtship dances. When he shared this with Divya and Dinesh, the two behavioural ecologists grew instantly interested in investigating this further. Divya was able to get the wheels rolling without much delay thanks to a grant from Azim Premji University, where she is a biology faculty.

Studying courtship 

The concept of sexual selection has fascinated scientists since it was first articulated by Charles Darwin over 150 years ago. ​“Whether this takes the form of a horn, a colourful display or a melodious vocal repertoire, they are meant to serve as a signal to the female that this male has ​‘good’ genes, worth passing over to the next generation,” says Divya. 

For many male spiders, there’s more at stake than the fate of their genes. Dinesh brings up the phenomenon known as sexual cannibalism where there is a chance that the male gets eaten by the female he is hoping to mate with. 

The male’s mating rituals therefore have to strike that perfect balance so that he can maximise his chance of procreating, or at the very least, survive to have a chance with another female. ​“This puts pressure on them and that’s why, I think, we see a huge spike in courtship patterns in jumping spiders and other such species.” 

The world of jumping spiders

Jumping spiders are a species-rich family, comprising over 6,600 species, as of 1 May 2024. The most famous of these, concerning courtship patterns, are the peacock spiders of Australia (Maratus species) and the paradise spiders of North America (Habronattus species). Now it seems that the Stenaelurillus spiders found in India may be another such group. 

Despite being geographically and evolutionarily distant, these three groups of jumping spiders have somehow converged on to this similar behaviour. How and why did this happen? Scientists in Australia and North America are already busy fitting some pieces of the puzzle together and Kiran feels it’s only right that Indian scientists do their bit by studying our group of nimble-footed arachnids.

Jumping spiders have another peculiar trait: their visual system is one of the best-developed among all invertebrates. ​“Most spiders are effectively blind, and are dependent on vibration and sounds for information,” explains Dinesh, who has previously investigated the visual abilities of these spiders and how it may benefit them during predator-prey interactions. He believes that this super ability may be the reason behind many of the jumping spiders’ unusual behaviours, including their colourful displays during courtship.

A herper enters the scene

As soon as the university grant was confirmed, Divya began to scope her networks for a Research Associate to take the lead on the experiments. She found a spark in a passionate young herpetologist named Shubham Soni. Nothing brought a spring to Shubham’s step like the mention of reptiles and amphibians, but his interest in colour and behaviour drew him to the spider project. 

Shubham knew he had his work cut out for him. Usually, scientists set out to characterise the behaviour of one species at a time, but here he was, tasked with comparing the courtship behaviours of four! He spent his first few months soaking up all the knowledge and skills he could from the scientists. Kiran visited the university and taught him to locate, identify and capture the different spiders; he learned from Dinesh to deploy various software as well as a high-speed camera to analyse spider movement; and Divya’s day-to-day mentorship helped him tune his brain to think like a behavioural ecologist.

Six months into the project, Shubham is hanging in there, enthusiasm intact. The spiders they are studying are very common. Two of them, S. sarojinae and S. lesserti, are frequently seen scuttling about within the university campus itself.

Shubham once found a whopping 30 individuals in just two hours of sample collection at Nandi Hills, but only nine in seven hours when he returned the following month. ​“The reason for the disappointing catch might have been because the short grasses in which these spiders are typically found had been burnt in the rocky-grassy hills where we do our fieldwork,” he surmises.

Setting the stage

Back in the laboratory, Shubham prepares a platform to experiment. This is usually an arecanut plate, strategically placed under bright lights and a camera. He then gingerly deposits a female spider on a dried leaf, positioning it in the most natural and inviting way possible. 

If you’re wondering how the female is so cooperative, the answer is somewhat gruesome. Shubham has to first render the female unconscious by exposing it to CO_2 or sacrifice it by freezing. This is admittedly his least favourite part, but it’s the only way he can record the action on camera. ​“If we stick to observations on the field, we may not need to sacrifice spiders, but that will take years. I want the science to come out and maybe this is the only way,” he reasons.

Once he has positioned the female spider, Shubham deftly releases a male onto the plate. In the best case scenario, the male will immediately detect the presence of a prospective mate and begin his colourful display. It turns out that the male spiders are sometimes desperate enough for a mate that they may not even notice the female is dead! 

Shubham remembers one happy morning when he got 12 recordings in a single session. Not all days are so productive, though. Usually, it’s a long and slow process of coaxing the male to get into the mood. Sometimes, changing the pose of the female or swapping the male for a more enthusiastic one may help. If even that doesn’t work, it may be worth checking if there were any identification errors. 

The differences between the females of the Stenaelurillus species are more subtle as compared to the more vividly coloured males. Could it be that Shubham was inadvertently trying to get a male attracted to a female of a different species? 

Until he can eliminate this possibility, the experiment has to be paused. The male is nudged back into its enclosure while Shubham turns to Kiran’s detailed descriptions of the spiders, back hunched and eyebrows furrowed. If there was indeed an error, he would heave a sigh of relief and quickly correct himself, but if not, he has to grit his teeth and move on. It would be just another bothersome reminder of how little we understand these omnipresent creatures.

Reading between the moves

The next step is analysis. Jumping spiders move incredibly fast but Dinesh’s high-speed camera makes it possible to track, and evaluate finer aspects of their dance such as the pace at which they move, how fast their legs vibrate and at which legs are lifted at what angle. ​“We don’t know the basis on which the female is judging, so we have to record and analyse everything,” states Divya.

Modern technology can help ecologists hear sounds once inaudible, see colours once invisible, and track movements that used to be too fast or slow. However, Dinesh cautions that there is a need for restraint. ​“For example, some of these spiders are brightly coloured. But before we hurry to use technology to quantify this colour, we need to know for sure that the spiders can see those colours. If they can’t, then it may not be relevant, at least in terms of courtship.”

Being the one at the site of action, Divya witnesses the ups and downs from close quarters. ​“There were phases when things weren’t working as planned,” she admits. While there is no doubt their experiments have immense scientific value, she has to constantly remind herself and Shubham that there needs to be an output as well. ​“How do we bring everything together? We are hoping to write a larger paper to tell this story.”

However the story pans out, their project is a silver lining at a time when things aren’t great for taxonomy, the science of naming, describing and classifying organisms. ​“It’s not taken seriously as a science,” rues Kiran. ​“The few of us who do this struggle to get good jobs and many end up leaving the field.” This is a shame because taxonomy is crucial to recognise and keep track of our biodiversity. Within the jumping spider family itself, there are likely thousands of species yet to be discovered, at risk of going extinct before they ever are. 

But even a realist like Kiran sees light at the end of the tunnel. ​“Amidst the rapid loss of biodiversity (and taxonomists!), the advancement of taxonomic research greatly depends on collaborations,” he writes in his website. And what better example of teamwork between experts from various domains than this one, between a taxonomist, two behavioural ecologists and a herpetologist who is now a full-time spider enthusiast! 

About the author

Nandita Jayaraj is a Science writer and Communications Consultant at Azim Premji University.